Testing the human color sense has meaning in the field of medicine for humans who work in certain areas of traffic or techniques wherein a recognizing of colored optical signals is important. The capability of testing the color-differentiating capability of humans is in practice particularly important in the red-green range.
The tests of the human color sense are today carried out mostly by pigment samples (for example, so called pseudoisochromatic tables), with transparent color filter glasses (color test plate) or by mixing and comparing spectral lights with the anomaloscope according to Nagel.
The anomaloscope of Nagel determines the capability of seeing colors in relationship to the seeing of red-green. The determination is made by comparing a binary mixture of a red and a green spectral light with a monochromatic yellow. From the mixture ratio and the adjusted luminous density of the comparison yellow, it is possible to recognize the color emmetropia of the person being tested with respect to seeing red-green. The anomaloscope according to Nagel has a mechanically very expensive construction. The red-green mixture is effected by two parallel inlet gaps, the outer gap jaws of which are nonchangeably fixed and are adjusted to the red or green wave length. The inner edges of the gap are formed by a common gap jaw which is movable by means of a fine adjustment screw. By moving the fine adjustment screw, the one gap is enlarged by the same amount as the other one is restricted and thus the mixture ratio of the two spectral lights can be varied. Next to the two mixing gaps there is arranged a third, unilateral gap for the comparison light, which is adjusted to the yellow color and by means of a movable gap jaw opens the yellow gap toward the long-wavelength side. The screws for adjusting the gap have scales. When the gap is closed, the scale shows 0 and when the gap is fully open the value 87. The usable width for the two mixing gaps is 73 intervals. In the position 0 the red gap is closed and the green gap is fully open, while in the position 73 the green gap is closed and the red gap is fully open. The produced light extends through a complicated optic into the eye of the viewer, so that the viewer sees in the lower half of the field of vision the homogeneous yellow and in the upper half, depending on the position of the mixing gap, a homogeneous red or a green spectral light or a mixture of the lights. The setting on the anomaloscope and its adjustment occurs according to the DIN norm 6160. However, an anomaloscope according to Nagel is decidedly complicated and expensive.
It also has already been suggested to use luminescence diodes for color tests, whereby two diodes of the same color are used, the brightnesses of which are modulated. If one modulates the lights of the wave lengths of the two luminescence diodes in opposite directions, that is, if one permits the one to light up, while the other one goes dark, and vice versa, then the intensity of the lights must be chosen accordingly, so that the one, who does not recognize anything in this spectral range, does no longer recognize a shimmer. However, the field of use is very limited, since a differentiating between anomaly and anopy cannot be determined with the method. Moreover, the device does not permit the common differentiation according to the Rayleigh equation, that is the determining of the anomal quotient.
The methods of testing with pigment samples and color filter glasses a high inexactness and thus not always usable results.
From Offenlegungsschrift No. 32 09 455 it is furthermore known to use two luminescence diodes for a device of the quantitative testing of the color sense and its disorders, whereby one luminescence diode emits a yellow light and the second luminescence diode is a so called two-color luminescence diode, which emits both a red and also a green light. By mixing the red and the green, substantially monochromatic, light sources it is possible to simulate the color frequencies in the red-green range. In the practical design of such a device, the two luminous diodes are arranged relatively close to one another, such that the person being tested must judge these two luminous diodes with respect to their color characteristic and brightness. Experience has shown that the measured values obtained with such a device cannot be compared with the standardized values which are fixed in the norm.
The basic purpose of the invention is to provide an anomaloscope of the abovementioned type such that the same permits a standard testing corresponding with the anomaloscope of Nagel. In comparison to the known anomaloscope, our design is substantially simpler and thus less expensive to manufacture and offers the possibility of providing the person being tested a neutralizing white stimulus field between the individual measurements.
The inventively constructed anomaloscope for testing the human color sense has a partially translucent mirror arranged in the optical axis of a beam-splitting cube, the beam-splitting cube has the advantage that an equality of the optical light paths exists, while in the case of the partially translucent mirror, the paths of the rays are optically not equal. The portion of the rays which has been let through, extends through an additional path of glass, experiencing a parallel shifting. Opposite this disadvantage stands the fact that it can be manufactured less expensively. A beam-splitter plane of a splitting mirror of the beam-splitting cube is arranged approximately 45.degree. with respect to the optical axis. To produce the monochromatic yellow, green and red light, single-color luminescence diodes are preferably used. A single-color luminescence diode emits a light, the spectral range of which includes a relatively narrow band range. In order to obtain a still more narrow spectral range, it is preferable to arrange one or several band-stop filters in front of each luminescence diode.
It is also conceivable to use halide lamps in place of the luminous diodes. Interference filters are arranged before the halide lamps. Of course, the interference filters are significantly more expensive and show the disadvantage that these are not permanently constant.
To create the anomaloscope, two of the light sources are arranged parallel to the optical axis, such that the two light sources have the same opposite distance from the optical axis. A partition wall preferably arranged between these two light sources, so that they do not interfere with one another. A third light source is arranged perpendicularly to the two light sources, which third light source illuminates the same area of the beam splitter plane that is illuminated by the second light source, namely, the one wherein the colors are mixed. By using the splitting mirror of the beam-splitting cube, a mixing of the spectral colors and a mixing of the strengthening of one spectral color with a weakening of the corresponding other spectral color is facilitated in a relatively simple manner. The anomaloscope, according to the invention, offers in a simple manner a co-observing possibility, so that the rays exiting from the free side of the beam splitter plane can be observed, which rays are moved, if necessary, with the help of a surface mirror into a position suitable for the co-observer.
A further splitting mirror is preferably inserted into the optical axis of the anomaloscope, which mirror is arranged at 45.degree. with respect to the optical axis and through which a white stimulus field is blended in. The norm for carrying out the tests states that this white stimulus field must always be added after a test. The actual view provided for testing absolute adjustment width is seen by the person being tested for only about 2 to 3 seconds, while for determining relative adjustment width, a respective test view or field must be viewed up to a maximum of 15 seconds. Since the white stimulus field is to be viewed only for a relatively short time, and since a subsequent illuminating by a halide lamp, commonly used, is to be avoided, a shutter is arranged, according to the invention, behind the halide lamp for releasing the rays only for a predetermined time. The luminous diodes are turned off during this time. If further halide lamps are used for the production of the yellow, green and red spectral colors, further apertures are arranged in front of the lamps.